1. Field of the Invention
The present invention relates to a magnetic head provided with a sectioned magnetic field regulator cooperating with a magnetic field generating coil. Further, the present invention relates to a data recording apparatus incorporating such a magnetic head and to a magnetic head fabrication method.
2. Description of the Related Art
To handle the proliferation of ever-larger digital files, several data-writing techniques have been developed to enable the condensation of data into a small space in a data storage medium such as a magneto-optical (MO) disk. Among the techniques is xe2x80x9cmagnetic field modulation.xe2x80x9d To implement magnetic field modulation, a target region in the recording layer of an MO disk is heated up to a certain temperature near the Curie point by application of a laser beam, and then the heated region of the recording layer is exposed to the magnetic field generated by a coil. The applied magnetic field is modulated in frequency to control the direction of magnetization in the target region.
To achieve a high data transfer rate by the magnetic field modulation, it is necessary to drive the field-generating coil at high frequency. As known in the art, induced current generated in the coil increases in proportion to the product of the driving frequency and the coil inductance. Thus, to avoid a large induced current in a high-frequency driving mode, the inductance of the coil should be as low as possible. To provide a low inductance, the coil may need to have a small diameter. However, with the use of a small coil, it may be difficult to subject the target region of an MO disk to effective exposure to the magnetic field generated by the coil.
One approach to overcoming the above problem is suggested in JP-A-10(1998)-320863. Specifically, JP-A-10(1998)-320863 discloses a magnetic head shown in FIG. 7 of the present application. As illustrated, the conventional magnetic head includes a magnetic field regulating disk 90 and a coil 91 arranged close to but insulated from the disk 90. With such an arrangement, the disk 90 is magnetized by the coil 91 being energized, and an appropriate magnetic field is applied to the laser-irradiated target region in the recording layer of the MO disk.
While the above magnetic head is functional in many respects, it still suffers the following drawbacks.
When the coil 91 is operated at a high frequency, an eddy current is induced in the field regulating disk 90 in response to the variation of the magnetic field. Due to the induced current, heat is generated in the field regulating disk 90, to eventually raise the temperature of the coil 91. When overheated, the coil 91 may be damaged or even broken due to e.g. xe2x80x9celectromigrationxe2x80x9d. Further, when the temperature of the coil 91 rises, the electric resistance of the coil 91 also increases. In this situation, the coil 91 needs more power for providing the required magnetic field. Disadvantageously, the increased power will additionally heat up the coil 91, which may hasten the breakage of the coil 91.
The present invention has been proposed under the circumstances described above. It is, therefore, an object of the present invention to provide a magnetic head in which the amount of induced current generated in the magnetic field regulator is reduced, whereby the temperature rise in the field regulator and the coil is properly controlled. Another object of the present invention is to provide a fabrication method whereby a magnetic field regulator used for such a magnetic head is easily made.
According to a first aspect of the present invention, there is provided a magnetic head that includes: a coil that generates a magnetic field and has an axis; and a magnetic member spaced from the coil along the axis and formed with a center hole. The magnetic member includes a plurality of sections that are electrically insulated from each other and arranged around the above axis.
With such an arrangement, it is possible to reduce the unwanted heat generation caused by the induced current in the magnetic member. As a result, the temperature rise in the coil is properly controlled, whereby the damaging of the coil and unacceptable increase in power consumption are avoided.
Preferably, the sections may be separated from each other by gaps extending radially from said axis. Each of the gaps may be filled with dielectric material.
Preferably, the magnetic member may be positioned farther away from a data storage medium than the coil is. As a result, the coil is arranged between the data storage medium and the magnetic member.
Preferably, the magnetic head of the present invention may further include a dielectric layer that encloses the coil and the magnetic member.
Preferably, the above sections may have a minimum width that is no smaller than the thickness of the sections and no greater than twice the thickness of the sections.
Preferably, the magnetic member may include a first magnetic layer and a second magnetic layer that is stacked on the first magnetic layer via a dielectric layer.
Preferably, the magnetic head of the present invention may further include an objective lens for forming a beam spot on a data storage medium. In this instance, a light beam emitted from a light source may first enter the objective lens, and then pass through the center hole of the magnetic member and the center of the coil, before it is reflected on the storage medium.
Preferably, the above-mentioned sections of the field regulator may be divided into a first group and a second group in a manner such that the first group sections and the second group sections are disposed to alternate with each other in the circumferential direction of the magnetic member.
Preferably, the magnetic head of the present invention may further include a dielectric film for covering the first group sections. The dielectric film may provide a plurality of recesses between the first group sections. In these recesses, the second group sections are accommodated.
According to a second aspect of the present invention, there may be provided a method of forming a magnetic member on a substrate, wherein the magnetic member includes a plurality of sections separated from each other. The method may include the following steps.
First, a plurality of first magnetic sections, separated from each other, may be formed on a substrate. Then, a dielectric layer may be formed on the substrate to cover the first magnetic sections in a manner such that the dielectric layer defines a plurality of recesses between the first magnetic sections. Then, a second magnetic section may be formed in each of the recesses.
In this manner, the first magnetic sections can be formed at a wide pitch that is sufficient to accommodate the second magnetic sections to be formed later. Thus, the forming operation of the first magnetic sections is performed easily. After the completion of the first sections, a dielectric layer is formed to cover the first sections. Thus, the second magnetic sections to be formed will not be electrically connected to the first magnetic sections. Since there is no need to worry about the short-circuiting with the first magnetic sections, the second magnetic sections can be formed readily with a small pitch with respect to the prefabricated first magnetic sections.
Preferably, the first and the second magnetic sections may be formed by plating.
According to a third aspect of the present invention, there is provided a magneto-optical data recording apparatus that includes: a spindle motor for rotating a magneto-optical data storage medium; a light source for irradiating the storage medium with a light beam; a magnetic head that includes a magnetic field generating coil and a magnetic member, the coil having an axis, the magnetic member being spaced from the coil along said axis and formed with a center hole; and an optical detector that detects reflection light from the storage medium and outputs a detection signal. The magnetic member includes a plurality of sections that are insulated from each other and arranged around said axis.
Other features and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings.